ammonoid

[ am-uh-noid ]

noun

1. any cephalopod mollusk of the extinct order Ammonoidea, from the Devonian to the Cretaceous periods, having a coiled, chambered shell.

ammonoid

/ ăm′ə-noid′ /

1. Any of various extinct cephalopods of the subclass Ammonoidea living from the Devonian to the Cretaceous Periods. Ammonoids had a symmetrical, coiled, chambered shell with angular sutures between the chambers. They are closely related to the nautiloids, including the modern-day chambered nautilus.

Word History and Origins

Origin of ammonoid¹

1880–85; < New Latin Ammonoidea, equivalent to Ammon ( ites ) name of the order + -oidea -oidea; ammonite ²